It is well known to employ so-called dye forming couplers (hereinafter simply referred to as couplers) which are capable of forming yellow, magenta or cyan dyes upon a coupling reaction with oxidation products of aromatic primary amine developing agents, in order to form color images in silver halide color photographic materials.
The principle of color photography using couplers and conventional examples of couplers are described, for example, in T. H. James, The Theory of the Photographic Process, Fourth Edition, Chapter 12, Macmillan Co. (1977) and Research Disclosure, No. 17643 (December, 1978).
As is apparently described in the above mentioned literature, phenols and naphthols have been hitherto employed as cyan couplers. However, since indoaniline dyes formed from these couplers have a small molecular absorption coefficient, large amount of couplers are requested in order to obtain sufficiently high image density. This is apparently disadvantageous, with respect to cost and also undesirable in view of the adverse influence on photographic performance More specifically, the incorporation of a large amount of couplers into an emulsion layer leads to an increase in the thickness of the emulsion layer, which causes an increase in the scattering of incident light at image exposure, resulting in degradation of sharpness.
For the purpose of solving this problem, specific types of couplers have been proposed as described in EP-A-249453. These couplers are certainly superior to conventional phenol or naphthol type couplers in view of a large molecular absorption coefficient. However, it has been found that fastness of color images obtained by these couplers is so poor that they cannot be employed in practice.